Friday, 04 October 2013, 10:00 a.m.
Sala Grande Palazzina B via alla Cascata 56/C
Crystalline WGM resonator based Optoelectronic Oscillators, stabilization, phase noise characterization and frequency combs generation
Patrice Salzenstein and Yanne K . Chembo
CNRS / FEMTO-ST, Besançon (France)
Our work concerns experimental aspects of an optoelectronic oscillator (OEO) based on
intensity modulation and a high-Q disk resonator. OEOs are microwave photonics systems intended to
generate ultrastable radio-frequency signals with unprecedented phase noise performance. In our
configuration, the crystalline whispering-gallery-mode (WGM) resonator acts both as a frequency filter,
selecting the microwave oscillating frequency, and as an optical storage element. Another advantage of
our system resides in its compactness allowing for efficient control of the temperature. Laser needs to be
locked on the resonance. It can be realized by Pound Drever Hall technique. However it is interesting to
investigate OEO stabilization as an alternative by TeO2–crystal–based acousto-optic cells. A system was
developed at the laboratory by using a double delay line optoelectronic system operating at 1.55 μm
wavelength and designed for OEO phase noise characterization. We present how the phase noise is
determined and how the global uncertainty of this system is calculated.
In the second part of this lecture we review the recent developments on the topic of Kerr optical frequency
comb generation using WGM resonators. These combs are sets of regularly spaced spectral lines in the
optical frequency range, generated using ultra-high-Q WGM resonators with Kerr nonlinearity. In such
resonators, the nonlinear effect is enhanced by the long photon lifetimes, and four-wave mixing (FWM) in
this context allows for the creation and mixing of new frequencies as long as energy and momentum
conservation laws are respected. These combs are expected to provide optical signals with exceptional
amplitude and phase stability. This feature is expected to be particularly interesting for many aerospace
and communication engineering applications where such stability is critical. We discuss recent
theoretical developments which enable to investigate the temporal dynamics and phase locking
phenomena in these combs, and theoretical results are compared with numerical simulations and
experimental measurements. The technological interest of these combs for various microwave photonics
applications is also reviewed.
Keywords: Optoelectronic oscillator; WGMs optical resonators; Frequency combs; Temperature control; Phase noise.